This invention relates generally to an electrostatographic printing or copying machine which utilizes multiple toners, such as in the formation of multi-color images and more particularly, to cleaning systems using preclean corona current to assist in removing toner and additive film particle buildup on the photoconductive (i.e. imaging) member.
In a colored image forming apparatus, an electrostatic latent image which is to be developed by a predetermined color is formed on a photoconductor by an optical system of a copying machine or printer. Then, the electrostatic latent image is developed by a developing unit which accommodates a predetermined colored toner to be used for development. This toner image may be subsequently transferred to a support surface such as copy paper or other medium to which it may be permanently affixed by heating or by the application of pressure. After each transfer process, the toner and other debris particles (i.e. residual particles) remaining on the photoconductor are removed from the photoconductor by a cleaning device.
The preclean latitude of a cleaner is defined by evaluating performance at a number of preclean current values. A setpoint is chosen by stressing the input to the cleaner and choosing the point upon which the latitude converges. This is a fairly straightforward process when single toner type systems are used. However, when multiple toner types are used a problem is encountered because of the potential for the latitudes to converge to different preclean current setpoints. This has been observed, for example, in cleaning latitude tests conducted on a Xerox 5090 with one color station added. In the Xerox 5090, the additional color station developed red toner as highlight color. The black toner preclean current setpoint convergence was different than for the red toner in the Xerox 5090 machine.
The following disclosure may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,206,687 to Suzuki et al. discloses a cleaning device having a doctor blade for peeling off toner, that has been de-electrified by the preclean corotron, from the photoreceptor drum.